Class I Injection Wells
WHAT IS A CLASS I WELL?
Class I wells inject hazardous and non-hazardous wastes into deep, isolated rock formations that are thousands of feet below the lowermost underground source of drinking water.
Class I injection wells inject far below the lowermost aquifer. Injection zones typically range from 1,700 to more than 10,000 feet in depth. The injection zone is separated from any aquifers by an impermeable “cap” rock called the confining layer, along with additional layers of permeable and impermeable rock and sediment.
CLASS I WELLS IN OHIO
Three facilities in Ohio currently operate a total of ten Class I injection wells regulated by Ohio EPA. Vickery Environmental (4 wells) operates a commercial waste disposal facility, receiving many types of waste from multiple sources. Innovene USA (4 wells) and AK Steel (2 wells) dispose of wastes generated on site during normal manufacturing operations. Fact sheets are available for the three active Ohio Class I injection well facilities:
WELL SITING AND CONSTRUCTION
Owners and Operators of Class I injection wells are required to apply to Ohio EPA for a permit for each well:
Permits are granted only after extensive data review followed by issuance of draft permits open to public comment.
All Class I wells have strict siting, construction, operation and maintenance requirements designed to ensure protection of the uppermost source of drinking water (USDWs). Wells injecting hazardous wastes have siting requirements to show that, with a reasonable degree of certainty, there will be no migration of hazardous constituents from the injection interval.
COMMONLY ASKED QUESTIONS ABOUT CLASS I INJECTION WELLS
Where does the waste come from?
Wastes are generated from a variety of sources ranging from steel mill operations to plastics production to manufacturing of agricultural chemicals. Some wastes are a product of other waste disposal methods (landfill leachate) or anti-pollution devices (wastewater generated by air pollution control equipment).
Why are the wastes not recycled?
Recycling of wastes, while on the rise throughout industry, is not always the most cost-effective means for businesses to manage waste waters. Further, some wastes are difficult to reclaim or technology simply does not yet exist to recycle the material. Another option available to industry is to reduce the amount of wastes generated.
For facilities operating a Class I injection well, pollution prevention is a required component of facility operations. Each facility is required per Section 6111.045 of the Ohio Revised Code to prepare and adopt a pollution prevention plan to identify technically and economically feasible measures that will be taken to reduce the amount of wastes generated at the facility. The facilities pollution prevention plan must be updated every three years.
Where do the injected wastes go?
Wastes placed in the injection interval displace the salty ground water or brines naturally contained in the pores of the rock formations near the wellbore. With continued injection, the brines are pushed farther from the well by the enlarging plume of wastes which is roughly cylindrical in shape. As a simplified example, an injection interval one hundred feet thick and containing ten percent pore spaces, would accept nearly 60 million gallons within a five hundred foot radius of the well.
How much waste can be injected?
Class I wells are sited only in areas where the injection interval and confining zone are very extensive laterally. Thus, if injection of fluids does not create substantial increases in formation pressure which cause the injection pressure limitations to be approached, many wells (or injection interval) have nearly unlimited capacity. However, Class I hazardous wells do have volume limitations placed on them based on computer modeling performed during the No-Migration demonstration.
Will pressure in the injection interval increase until the well or rock fails?
With injection over many years, a slow buildup of pressure usually occurs in the injection interval. Pressures are highest near the well and decline rapidly at increasing distances from the well. However, because the injection interval is so extensive, injected fluids can continuously flow away from the well, thus preventing a great buildup of pressure near the well. For this reason, when injection ceases, pressures in the injection interval slowly return to near original pressures further demonstrating the rock formation's ability to accept the injected fluids. Additionally, injection pressure limitations prevent injection at pressures which could cause fractures in the injection or confining zones.
How does Ohio EPA know that the wastes stay where they are injected?
Information reviewed in as part of the permitting process and in demonstrations allows a determination, with reasonable certainty that injected fluids will remain in the permitted intervals. Additionally, periodic testing is required to be performed by operators to ensure that there is no movement of fluids into a USDW. These procedures are witnessed by Ohio EPA and results of all tests are subject to Ohio EPA's review and approval.
There are numerous tests to determine fluid movements; one test uses a temperature sensor run through the length of the well to identify zones which have accepted fluid. Testing with an advanced microphone system allows recognition of flow behind cemented casing. Annual pressure fall-off testing provides information on the condition of the injection interval including the presence or absence of fractures. Finally, ground water monitoring is also conducted at facilities. Monitoring wells are used to observe ground water quality in the lowermost USDW or to monitor pressure and chemistry in deeper zones above the injection interval.
How does Ohio EPA know what is being injected?
Each facility is required to conduct routine sampling and chemical analysis of their injectate and to report the results to Ohio EPA. The agency also conducts additional sampling on a limited basis.